docs: def get_file(self, filename, dir='static'):
          """
          get_file will search from apps directory
          """
          if os.path.exists(filename):
              return filename
          dirs = self.apps
          if dir:
              fname = os.path.join(dir, filename)
          else:
              fname = filename
          for d in reversed(dirs):
              path = pkg.resource_filename(d, fname)
              if os.path.exists(path):
                  return path
          return None